On the performance of a nonorthogonal multiple-access technique for downlink MIMO cooperative networks
Additional Document Info
Copyright 2017 John Wiley & Sons, Ltd. Nonorthogonal multiple access (NOMA) has been regarded as an appropriate multiple-access technique for fifth generation due to its radio-frequency spectrum effective usage and significant capacity gains. In this paper, a cooperative network is considered, where 2 kinds of signal transmission links exist at the same time, ie, the direct link and the relaying link. The system performance is evaluated in a NOMA-based downlink multiple-inputmultiple-output relaying network in terms of 2 measures, ie, the outage probability and the ergodic rate. Due to the uncertainty of the signal-to-interference-plus-noise ratio (SINR) at the users reached by the direct links, at the base station, the best antenna that maximizes the instantaneous system SINR at the relay is selected to transmit the signals. Furthermore, for the receiving antennas at the multiple users, maximal ratio combining is used to exploit efficiently the diversity offered by the multiple antennas. Closed-form expressions for the exact outage probability and the ergodic rate at high SINR are derived. Moreover, the diversity order is obtained by analyzing the asymptotic outage probability. Finally, the extensive simulations are performed to corroborate that NOMA, in combination with a successive interference canceller, represents a significant alternative to the orthogonal multiple access in catching up with the high demands for radio spectrum.